Incorporated herewith by reference is U.S. Pat. No. 4,223,654.
The invention is based on an electronic regulating device for rpm regulation in an internal combustion engine having self-ignition in accordance with rpm, fuel quantity, and accelerator-pedal position having a PI (proportional-integral) regulator and a comparison circuit for instantaneous set-point and idling rpm.
Regulating devices of this kind should function as rapidly as possible, and to this end they exhibit very steep characteristic curves. An electronic rpm regulator with PID (proportional-integral-differential) functioning is known; it has a control capacity for the proportionality range from zero up to approximately 10%. This is attained in the known regulator by varying the set-point rpm value, as the input variable of the regulator, in accordance with the actual value of load (resp. injected fuel quantity).
In electronic P-regulators (proportional action controllers) with purely proportional functioning and very steep characteristic curves, the danger of instability has been demonstrated. In view of the safety, reliability and good driveability which are required in internal combustion engines with self-ignition, this instability is highly undesirable.
The proposed regulating device, which controls rpm, in accordance with fuel quantity, accelerator pedal position and rpm, is provided with a PI regulator which is dependent on rpm deviation assuring the requisite stability even in the case of very steep characteristic curves. Now such steep characteristic curves can be achieved in electronic regulators with same or better performance and higher flexibility compared with pure mechanical systems.